ECG lead systems are used to obtain biopotential signals containing information indicative of the electrical activity associated with the heart and pulmonary system. To obtain biopotential signals, ECG electrodes are applied to the skin of a patient in various locations and coupled to an ECG device, e.g., an “ECG monitor” or “ECG telemetry.” Placement of the electrodes is dependent on the information sought by the clinician.
The placement of the ECG electrodes on the patient has been established by medical protocols. The most common protocols require the placement of the electrodes in a three-lead, a five-lead, or a twelve-lead configuration. A three-lead configuration requires the placement of three electrodes; one electrode adjacent each clavicle bone (RA, LA) on the upper chest and a third electrode adjacent the patient's lower left abdomen (LL). A five-lead configuration requires the placement of the three electrodes in the three-lead configuration with the addition of a fourth electrode adjacent the sternum (Va) and a fifth electrode on the patient's lower right abdomen (RL). A twelve-lead configuration requires the placement of ten electrodes on the patient's body. Four electrodes, which represent the patient's limbs, include the left arm electrode (LA lead), the right arm electrode (RA lead), the left leg electrode (LL lead), and the right leg electrode (RL lead). Six chest electrodes (V1-V6 leads) are placed on the patient's chest at various locations near the heart. Three standard limb leads are constructed from measurements between the right arm and left arm (Lead I), the right arm and the left leg (Lead II) and the left arm to left leg (Lead III). Other conventional lead configurations include a 14 leads system that incorporated additional leads located on a back surface.
An ECG lead set typically includes an array of three, five, or twelve leads as determined by the intended clinical protocol. Each individual lead wire includes, at a patient end thereof (e.g., distal end), an ECG lead wire connector configured to operably couple the lead wire to an electrode pad affixed to the body of a patient. At the opposite (e.g., proximal) end, the individual lead wires are gathered into a common coupler that is configured to operably couple the array of lead wires to an ECG device. Leads sets are typically provided with a generous length of lead wire sufficient to reach from the patient to the ECG device. In some instances, however, the lead wire may fall short, in which case a lead wire extension cable having appropriate distal and proximal couplers may be employed. In some instances, the lead wire coupler of an ECG lead set and/or ECG lead extension may be incompatible with an available ECG device, in which case an ECG adapter may be employed that facilitates operable coupling of the otherwise-incompatible physical and/or electrical characteristics of the disparate couplers.
Radio frequency interference (RFI), sometime referred to as electromagnetic interference (EMI), is a disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of a circuit. Biopotential signals are generally very low-level signals, and a typical ECG device has a very high input impedance. As a result, biopotential signals may be susceptible to RFI, particularly from devices that may be in use concurrently in a clinical environment, e.g., an electrosurgical instrument, or a microwave ablation unit. RFI may be exacerbated when an ECG lead wire extension cable is used.